Not so long ago, I went with my girlfriend to watch "Red Cliffs". She was somewhat disturbed by the main characters' over the top fighting style – even though it was rather tame by Chinese standards – but what surprised her was that the film was based upon historical events. In 208 AD, the combined forces of the southern warlords Liu Bei and Sun Quan defeated the numerically superior army of Cao Cao, making sure that China would remain divided into three distinct polities for the next sixty years. It was an event of tremendous importance in the history of China, and therefore of the world, and it is only because of the ethnocentrism of the French educational system so few people know about it.

Yet, its European counterpart, the Battle of Chalons, is still less known. I am not talking, of course of the second Battle of Chalons, where Aetius and his hodgepodge romano-germanic army defeated Attila's no less hodgepodge germano-hunnic army, but of the first one, where Aurelian forced the surrender of the last Gallic emperor Tetricus the First, ensuring the Roman Empire will remain united... and collapse far more completely than China ever did.

That is where those ancient battles matter for us, men of the twenty-first century, at the eve of a collapse quite similar to the one which befell the Roman and the Han Empires.

Societal collapse nearly always translates into political disintegration. It is a normal consequence of the way complex society works. Whenever a polity increases in size, the percentage of its resource base it has to devote to its internal functioning increases as well. As long as the increase in productivity or gross resource base makes up for it, all goes well, but the law of decreasing returns means that at some point the polity is caught between rising costs and stagnating incomes. Its net resource base, the one it can mobilize to face an emergency shrinks and it slowly loses the control of its territory. It can then be taken over by foreign invaders, or disintegrate as warlords or local governments seize effective control of the territory. The net result is always the same : a large polity, endowed with large potential resource it can no longer mobilize is replaced by smaller polities, with a smaller resource base but a better mobilization capacity.

That is what happened in the third century AD in both China and Europe and the outcome of this crisis is quite edifying. It was what John Michael Greer calls a maintenance crisis, a temporary, self-limiting, overshoot and it remained so in China. Cao Cao, the northern warlord failed to reunify the Han Empire, and the one Chinese Empire was replaced by three, leaner and more efficient, kingdoms which laid the foundations for the Jin dynasty.

In Europa, however, the Palmyrene and Gallic breakaway states couldn't ally and were separately defeated by a resurgent Roman Empire, which then reorganized and proceeded to exploit more efficiently – that is more ruthlessly – its resources. The result was a longish period of relative stability, followed by a depletion crisis which tore away the very fabric of Western European society.

We are at the eve of a depletion crisis. Present day polities are so complex – and therefore costly – they cannot exist without a constant inflow of energy only fossil fuels can provide. With the advent of peak-oil, they will less and less able to pay for the cost of their existence and will disintegrate. The way they will do it, however, will matter quite a lot and if they cling to their unity too long and fail to decentralize, they will only exhaust resources their successor will need to firmly establish themselves. So instead of the warring but reasonably stable Three Kingdoms, we will end up with squabbling fiefdoms.

This is, I think, a vital task peak oil activists unfortunately tend to overlook : how to make sure that when current polities fail, they won't be replaced by a reincarnation of the petty kingdoms of England. That certainly does not mean encouraging every wild secessionist scheme – some are reasonable project, as in Scotland, Wales or Catalonya but most others are just recipes for disasters – but encouraging decentralization, growth of regional identities and empowerment of local authorities, so that, when the time will come, we won't need a Battle of the Red Cliffs to avoid fighting the one of Badon Hill.